Re-growth of GaN buffer layer on nanoporous GaN at different chamber temperature of 750, 850 and 1000C were used to study the mechanism behind threading dislocations reduction in the GaN film subsequently overgrown. The growth of a 100nm GaN buffer layer at 850C causes dislocations to bend into the underlying GaN and annihilated at the interface of GaN buffer/nanoporous GaN. Thermal treatment of nanoporous GaN in MOCVD growth chamber at 850C in NH3 and N2 ambient leads to the pinning of the threading dislocations at its surface edge steps by impurity -vacancy complexes of SiNx. The SiNx were formed by the impinging adatoms of NH3 which interact with Si dangling bonds at the sub-grain boundaries of the nanoporous Si-doped GaN. When the nanoporous GaN sample undergoes rapid thermal annealing in N2 ambient, no effective filling of these voids were observed and dislocations density was not substantial reduced. Re-growth of GaN at 850C re-structured the nanoporous GaN, forming a SiNx complex at the voids or pores which pinned dislocation propagation. This explained the mechanism behind dislocation annihilation in re-grown GaN on nanoporous GaN template with the use of additional interfacial GaN buffer layer.

Threading Dislocations Annihilation in Regrown GaN Film on Nanoporous GaN Template. C.B.Soh, H.Hartono, S.Y.Chow, S.J.Chua, S.Tripathy: Physica Status Solidi C, 2009, 6[S2], S699-702